The compound 2-KGA(2-keto-L-gulonic acid) is an important precursor for Vitamin C. Reactions to convert L-sorbosone to 2-KGA are known. In fact 2-KGA production from L-sorbosone using cell free extracts of microorganisms was reported in several prior publications. In U.S. Pat. No. 3,907,639, microorganisms belonging to the genus Acetobacter, Pseudomonas, Escherichia, Serratia, Bacillus, Staphylococcus, Aerobacter, Alcaligenes, Penicillium, Candida and Gluconobacter were reported to be capable of such a conversion. Furthermore, Kitamura et al., Europ. J. Appl. Microbiol., 2.1, (1975) reported that the L-sorbosone oxidizing enzyme found in Gluconobacter melanogenes IFO3293 required neither coenzyme nor an electron acceptor for the development of enzyme activity. Makover et al., Biotechnol. Bioeng. 17, 1485, (1975) reported the presence of L-sorbosone dehydrogenase activity in the particulate fraction of Pseudomonas putida ATCC 21812. However, the L-sorbosone dehydrogenase has never been isolated from Pseudomonas putida in the form of a homogeneous protein. Therefore, the physico-chemical properties of the enzyme have not been specified yet.